Sewing machine



Oct. 9, 1956 G, ATTWQOD ET AL 2,765,759

SEWING MACHINE ,Filed Dec. 17, 1952 3 Sheets-Sheeyl JOHN G. ATTwooD SALVATORE LIPPERE ATTORNEY ct. 9, 1956 J, G, ATTWOOD ET AL 2,765,759

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JOHN G. ATTWOOD ATTORNEY 0t.9,195e J. G. ATTWQOD TAL K 2,765,759

SEWING MACHINE Filed Dec. 17, 1952 3 Sheets-Sheet 3 E f//fnimn'lf Q 1% 3 n @Film m .f f f y Illlllllilllllllllll) Q// i m f., :nl `m xm Os 5\N s i BK) LL- IN V EN TORS. JOHN G. TTWOOD SALVATORE LIPPERE ATTORNE SEWING MACHINE Application December 17, 1952, Serial No. 326,498

8 Claims. (Cl. 112-220) The present invention relates to sewing machines adapted for operation at high speeds and more particularly to means for isolating or suppressing the transmission of torsional vibrations set up in moving members in one portion of a sewing machine to interconnected moving members in another portion of the machine.

In sewing machines operated at high speeds, torsional vibrations are set up in rotating or oscillating shafts which serve to reciprocate or oscillate certain driven elements. For example, in reciprocating a needle bar, the rotating driving shaft starts the needle bar from a standstill at the top of its stroke and accelerates it to a quite high speed at the middle of the stroke. The force required for this purpose causes twisting of the driving shaft in one direction. At the bottom of the stroke, the needle bar must be slowed to a stop and this deceleration causes twisting of the shaft in the other direction. Two similar twisting forces are imparted to the driving shaft in moving the needle bar from the bottom to the top of its stroke. The driving shaft thus receives two twisting cycles for each revolution.

It has been found that these torsional or twisting forces tend to be transmitted through the driving connections to other driven portions of the sewing machine where they may cause excessive wear. For example, many vertical axis rotary hook lockstitch sewing machines are provided with a power driven top shaft arranged to drive a lower shaft through a gear train, the lower shaft, in turn, driving a pair of vertical axis rotary hooks through spiral gears. In such machines, particularly when operating at high speeds, it has been observed that the vibratory forces set up in the upper shaft, through needle bar inertia effects or otherwise, are transmitted to the spiral gears with resultant noise and excessive wear of the spiral gears.

Accordingly, the principal object of the invention has been to provide a high speed sewing machine in which torsional vibrations set up by one or more driven reciprocatory or oscillatory members of the machine are not transmitted to other driven parts in the machine.

More particularly, it has been an object of the invention to provide a sewing machine in which a driving shaft is suitably coupled to a driven shaft to impart rotary motion thereto, the coupling means being so constructed and arranged that the driven shaft is isolated from the driving shaft with respect to vibratory components of the motion of the driving shaft. The vibration isolation to which reference is made herein should be distinguished from shock isolation which involves much higher frequencies in a machine of the character with which the present invention is concerned. Vibration isolation in accordance with its recognized technical meaning requires the introduction of sufficient flexibility into the system which is to be isolated to drop the resonant frequency of this system appreciably below the frequency of the vibrating force to be isolated.

' A specific object of the invention has been to provide a lockstitch' sewing machine n which' torsional vibrations 2,765,759 Patented Oct. 9, 1956 set up by reciprocation of the needle bar are not transmitted to the rotary hook and the gears for driving the hook shaft.

Toward the foregoing ends, a feature of the invention is the provision in certain rotary driving connections of a sewing machine of means for isolating or suppressing the transmission of torsional vibrations.

Another feature of the invention involves the provision of isolating means of the character indicated which will introduce flexibility into the sewing machine driving connections, the flexibility being such as to cause the critical or natural frequency of vibration of the driving connections to ditfer from the frequency of the vibrations imparted to the connections by the parts driven thereby.

A specific feature of the invention is the provision in a lockstitch sewing machine of improved coupling means for transmitting power from an upper main shaft to a rotary hook shaft, said coupling means serving to isolate the hook shaft from the upper main shaft with respect to torsional vibrations,

Other and further objects, features, and advantages of the invention will appear from the following descriptlon.

A sewing machine constructed in accordance with the invention may comprise a plurality of cooperating stitch forming and work feeding elements and driving connections therefor, the driving connections including a plurality of shafts and means intercoupling the shafts so that rotation of one produces rotation of the other, a flexible element being included in the coupling means to isolate the two shafts in relation to eachother with respect to the Vibratory forces set up therein. These vibratory forces or periodic reversals of force may be set up in various ways. As pointed out hereinbefore, one source of these forces is the inertia effects produced by reciprocation of a needle bar.

The invention will now be described in greater detail with reference to certain illustrative embodiments thereof shown in the appended drawings, in which:

Fig. l is a longitudinal sectional View of a sewing machine embodying the invention;

Fig. 2 is an inverted plan view of the machine of Fig. l with the bottom cover plate of the oil reservoirremoved;

Fig. 3 is an enlarged perspective view, partly in crosssection, illustrating the lower, driven shaft and the driving and vibration isolating means therefor;

Fig. 4 is a transverse sectional View taken along the line 4 4 of Fig. 2;

Fig. 5 is a vertical sectional view, similar to a portion of Fig. l, illustrating a modified form of coupling and vibration isolating means according to the invention;v and Fig. 6 is an exploded view of the coupling and isolating means of Fig. 5.

While the invention will be described in connectionwith a vertical axis, rotary hook sewing machine constructed generally in accordance with the teachings of U. S. Patent No. 2,329,484, issued September 14, 1943, to Oscar Quist, it should be understood that the invention is not limited to this type of sewing machine but will find application in many types of sewing machines.

Referring now to the drawings, the illustrative machine comprises a frame having a base or work supporting portion 10, a vertical standard 11, and an overhanging arm 12 terminating in a needle head 13. Power is supplied to the machine through a combined handwheel and pulley 14 adapted to be connected by a belt with an electrical transmitter, or any other suitable source of power. This pulley is secured to a main drive shaft 15 which extends through the end wall of the vertical standard 11, near its top, and longitudinally through the overhanging arm 12 into the needle head 13. l

-Bearing'bush-ings 16 and 17 are set intospac'edtra'ns# verse partitions 18 and 19 within the overhanging arm 12. An oscillating sleeve 2i) is journaled adjacent the ends thereof in the bearing bushings 16 and 17. Within the opposite ends of the sleeve 2li are provided bushings 21 and Z2, respectively, which serve as bearings for the shaft A crank member 23 is mounted on the end of the shaft 15 within the needle head 13. A pitman 24 is connected at its upper end to a crank pin 25 carried by member 23 and at its lower end is provided with a sleeve portion 26 adapted to receive an inwardiy projecting stud 27 of a collar 28 secured to a needle bar 29 to impart endwise reciprocatory movement to the needle bar in response to rotation of the shaft i5. At its lower end, the needle bar 29 carries a head 3o to which may be secured one or more needles 31.

The needle bar 29 is mounted for longitudinal 1n.- ciprocation within a frame or carrier member 32 which is suspended from a pivot stud 33 carried by the machine frame adjacent the upper end of the needle head 1.3. A portion of the member 32 in Figs. l and 4 is broken away to show the collar 28.

lt will be understood that this broken away portion is yolted to permit attachment of the collar 28 to the needle 'oar 29 and to permit the needle bar 29 to execute its endwise reciprocatory movement. Member 32 is provided with a projecting portion 33 which is connected to a link 34 by means of a pin 35. Link 34 is connected to an arm 36 by means of a pin 37 (Fig. 4). The arm 36 is secured to the end of the sleeve 20 so that, as the sleeve 2li is oscillated, the member 32 together with the needle bar 25B will be swung laterally about the axis of the pin 33. This serves to carry the needles in the line of feed to provide a suitable needle feeding action. Oscillating or reciting movement is imparted to the sleeve 2i) through driving connections from the shaft 15. These connections, which are shown only in part herein, are preferably similar to those disclosed in the above mentioned Quist patent. They include an arm 49 rigidly aiiixed to the sleeve adjacent the end thereof located within the vertical standard 11. The lower end of arm 40 is forked to accommodate a block 41 pivotally a-flixed thereto by means of a pin 42. The block 41 corresponds with the sleeve 65 of Quist Patent No. 2,329,484 and is provided with a hole (not shown) arranged slidably to accommodate a vertically disposed rod forming part of a rocker assembly. This rocker assembly is not shown in the drawings but may correspond generally to the rocker 67 and associated parts shown in Fig. 6 of said Quist patent. The upper end of the rocker rod is slidably mounted in an offset sleeve portion (not shown) of a strap 4d. The bearing portion of the strap 44 encompasses a portion of an eccentric 45 which is secured to the shaft 15. The other portions of the needle feed mechanism, including the adjustable height pivotal mounting for the rocker rod, may be constructed generally in accordance with said Quist patent. The arrangement is such that swinging movement is Vimparted to the rocker rod through rotation of the eccentric 45, the swinging movement being translated into rocking movement of the sleeve 2i).

Arranged to cooperate with the needles 31 in stitch formation below a throat plate Si) (Fig. 4) is a pair of vertical axis rotary hooks 51 and 52 (Fig. 2). Secured to the shafts 53 and S4 (Fig. 2) of the rotary hooks 51 and 52, respectively, are spiral gears 55 and 56, respectively, which mesh respectively with spiral gears 57 and 58 secured to a rotating shaft 59. The gear ratios are such that the rotary hooks 51 and 52 rotate at twice the angular speed of the shaft 59. This shaft is suitably journaled within the base 10 of the machine and extends through a bearing 60 into an oil sump or reservoir 61 which may be lled with lubricant to a suitable level. The shaft 59 is arranged to be driven by a gear 62 through vibration isolating driving connections to be described in greater detail hereinafter in connection with Fig. 3. The gear 62 is included in a train of spur gears 62, 63 and 64 located within the hollow standard 11. The gear is rigidly aixed to the shaft 15 and drives the idler gear 63 which in turn meshes with and drives the gear 62. The gearing 62, 63 and 64 is such that the shafts 15 and 59 are rotated in the same direction and at the same speed.

Operating through slots in the throat plate 50 is a feed dog 76 (Fig. 4)- Which is adjustably secured to a feed bar 71. The latter has an arm which extends under the shaft 59 and which is pivotally connected to a strap 72 which surrounds an eccentric 73 carried by the shaft 59. Rotation of the shaft 59 imparts suitable up and down movements to the feed dog 7i) through the linkage described. At its rear end, the feed bar 71 is pivotally connected to a pin 74 at the top of a vertical rocker 75. This rocker is mounted on a shaft '76 which extends parallel with the shaft 59 below lthe work supporting surface formed by the top 0f the base 10. The shaft 76 is suitably journaled in bearings provided in the base l0 and extends into the oil sump 61.

A collar 77 having a laterally extending arm 78 is secured to the end of the shaft 76 within the sump 61. A connecting rod 79 (Fig. 1) is secured to the arm 78 by means of a ball land strap connection 80. The other end of the connecting rod 79 is secured through a ball and strap connection 81 to a rearwardly and laterally extending portion S2 of the bell crank lever 40. Rocking motion of the lever 46 thus imparts feed rocking move ment to the shaft 76 and, through the feed bar 71, to the feed dog 7?.

As the upper shaft 1S is rotated, endwise reciprocatory motion is imparted to the needle bar 29 through the pitman 24 and crank 23. By action of the eccentric 45, rotation of the shaft 15 also produces rocking movement of the sleeve 2i) and of the shaft 76. As a result, the needle bar frame member 32 is swung -to and fro in the direction of feed in synchronization with feed movements imparted to the feed dog 70. As explained hereinbefore, inertia effects caused by actuation of the needle bar 29 upon rotation of the shaft 15 sets up torisional vibrations in the shaft 15. Similar forces produced by movement of the parts driven by the eccentric 45 also tend to set up vibrations in the shaft 15. It has been found that these vibratory forces, which may be considered as components of movement superimposed on the normal rotation of the shaft 15, tend to be transmitted through the gear train 62, 63 and 64 to the shaft 59. These vibratory forces, if imparted to the shaft 59, would tend to produce excessive wear upon the meshing gears 55 and 57 and 56 and 53. This excessive wear would be caused by the inertia or momentum of the rotary hooks which tends to keep them going at a relatively constant speed, whereas the spiral gears 55 and 56 which drive the hooks would tend to slow down and speed up in response to the vibratory forces present in the shaft 59. Considering only the vibratory forces produced by reciprocation of the needle bar, it will be evident that the shaft 59 tends to speed up twice and slow down twice in each revolution of the shaft 59 because of the reversal of movement of the bar at the two ends of its stroke. Varying speed of the gears 55 and 56, fixed to the shaft 59, which would result from the transmission to them of the indicated torsional Vibrations wouldcause these gears to clash repeatedly with the gears 57 and S8, respectively thereby causing rapid wear of all of these gears.

In accordance with the invention, the driving connections for the shaft 59 are arranged to impart the desired rotary motion to this shaft but to isolate the latter from the torsional vibrations super-imposed on the rotary motion of the drivingl shaft 15. An illustrative form of the driving connections lis illustrated in detail in Figs. 1 and 3.

Referring now to these views, the gear 62, which meshes with and is driven by the gear 63, is so mounted on the shaft 59 as to be rotatable relative thereto. Axial movement of the gear 62 on the shaft 59 is prevented by means of a bushing S5 mounted in the machine frame adjacent one side of the gear 62 and a thrust collar 86 fixed to the shaft 59 adjacent an axially extending hub portion 87 of the gear 62. A disc 88 is affixed to the shaft 59 by means of a set screw 89 provided in an axially extending hub portion 90 of the disc. The gear 62 -an'd the disc 8S are provided with aligned holes `adapted to receive a pair of spring rods 91 and 92. The spring rods 91 and 92 preferably have a press fit in the respective holes in the disc 88 and have a sliding llt in the respective holes in the gear 62. lf desired they may have a press lit in both the gear and the disc and any foreshortening of the connection between these parts due to the flexing of the rods may be taken care of by a slight axial movement of the gear along the shaft 59. As the gear 62 is caused to rotate 4by rotation of the gear 63, the rotary motion imparted thereto is translated into rotation of the disc 88 and the shaft 59 through the spring rods 91 and 92. It will be observed that the coupling provided by the spring rods 91 and 92 will have a certain amount of flexibility. This flexible coupling between the gear train and the shaft 59 isolates the shaft 59 `from the shaft 15 with respect to torsional vibrations so that the shaft 59 will rotate at the same speed as the shaft but will be substantially free yfrom the vibratory components of motion superimposed on the rotary motion of shaft 15.

The extent of isolation achieved through the llexible coupling will, of course, depend upon the `amount of ilexibility provided. In general, it may be said that the greater the flexibility the greater the isolation that will lbe achieved. However, too great a `flexibility would permit the shafts 15 and 59 to get too far out of time with respect to their desired relative positions which would result in poor stitch formation and might cause the needles 31 to strike portions of their respective rotary hooks. It should also be observed that the introduction of flexibility into the driving connections :for the shaft 59 lowers the natural resonant frequency of the shaft and driving connections. It is important that the llexibility introduced shall not adjust the resonant frequency into the operating speed range of the sewing machine since, -if the natural resonant frequency were to coincide substantially with the operating speed, the wear problem would -be greatly aggravated. It has been found that the best operation is achieved when the natural resonant frequency of the driving connections and the shaft 59 lies within a range of about 1A to 2X1 of the normal operating speed of the sewing machine. Thus for a sewing machine which is normally operated at about 4,000 R. P. M., the flexibility should be adjusted so that the natural resonant frequency corresponds to about 1,000 to 3,000 vibrations per minute. A resonant frequency within this range will provide good isolation without interfering with stitch formation. In a preferred embodiment of the invention, a ilexible coupling of the type shown in Figs. l, 2 4and 3 was found to give the best results when the resonant frequency corresponded to about 1200 R. P. M., the operating speed being about 4,000 R. P. M.

Since the flexibility required to achieve the desired resonant -speed will be dependent upon the moment of inertia of the shaft to which the coupling is applied, when this moment of inertia is low -a fairly soft flexible coupling will be required. Alternatively, a relatively stiff flexible coupling may be used if the moment of inertia of the shaft is relatively high. For example, in the embodiment of the invention illustrated in Fig. 3, the disc 88 may be made to act as a ily wheel to increase the moment of inertia of the shaft 59.

The introduction of flexibility into the driving connections is not, of course, limited to the use of spring rods as illustrated in Figs. l, 2 and 3. Other suitable lflexible couplings may be employed. For example, in Figs. 5 and 6, there is shown a rubber coupling assembly for connecting the gear 62 (corresponding to the gear 62) and the shaft 59.

Referring now to Figs. 5 and 6, the gear `62' is mounted for slight relative rotation on Ithe shaft 59. Axial movement of the gear 62 toward the right in Fig. 5 is prevented by a Ibushing in the machine frame. The left side of the gear 62 in Figs. 5 and 6 is provided with -a circumferential slot or recess which increases in radial dimension to provide undercut circumferential edges, as best shown in Fig. 5. A yconnector 96, which may be formed of rubber or `other suitable flexible material, is provided with an lannular projection 97 on one side thereof that lits =snugly Within the recess 95 land is Ibonded to the surfaces of 'the latter. The `other side of the connector 96 lis provided with -a similar annular projecting portion 98 which fits `snugly within and is bonded to the surfaces of an annular recess, -similar to recess 95, provided in the ladjacent side of a disc 99. The opposite face of `the disc 99 is provided with threaded holes 100 which are aligned with holes 101 provided in a radially extending flange portion 102 of a `hub member 103. The flange 102 is held lirmly -against lthe adjacent face of the disc 99 by means of screws 104 extending through the holes 101 'and threaded into the holes 100. Hub member 103 is securely aflixed to the shaft 59 by means of set screws 105. As the gear 62' is caused `to rotate by its gear connection with the shaft 15, the rotary motion is imparted to the shaft 59 through the 'flexible connector 96, the disc 99 and the hub 103. The connector 96 should be constructed to provide the desired llexibilityl in thedriving connections so that proper isolation of the shaft 59 from torsional vibrations in the sha-ft 15 will be provided. At the same time, the flexibility should not be so great as to throw out the relative timing of the movements of the needle bar and the rotary hooks. Moreover, the considerations discussed in relation to the ilexible rods as to the natural resonant frequency of the system shouldbe observed.

While the invention has lbeen described in connection with specific illustrative embodiments thereof and in specic uses, it should be understood that it is not limited thereto since `obvious modifications thereof will occur to those skilled in the -art without departing from the spirit and scope of the invention as set for-th in the appended claims.

What is claimed is:

l. A high speed sewing machine comprising a plurality of cooperating stitch forming and work feeding elements and driving connections therefor, said driving connections including a first shaft, a second shalt, means intercoupling said shafts for rotation of the rst by the second, parts driven by said lirst shaft for operating certain of said elements, and parts driven by said second shaft for operating other of said elements in coordination with said certain of said elements to form a seam, said last mentioned parts .tending tto apply periodic reversals of torsional force to said second shaft at a frequency double the speed of rotation of said shaft, said intercoupling means having embodied therein means `for isolating the torsional vibrations inciden-t to said periodic reversals of force, said last mentioned means including at least one flexible element which has substantial flexibility sufficient to isolate torsional vibrations created by said periodic reversals of force but not of such flexibility as to disturb the coordinated relation of said stitch forming and work feeding elements'.

2. A sewing machine of the character set forth in claim l in which the flexibility of said at least one flexible member is such as to provide said rst shaft and the driving connection therefor with a natural resonant frequency substantially lower than said periodic reversals of torsional force.

3. A sewing machine of the character set forth in claim 1 which is adapted to operate at a given speed and in which the flexibility of said at least one exible member is such yas to provide said first shaft and the driving connection .therefor with a resonant frequency lying within a range corresponding to about one-fourth to three-fourths of said given speed. 4. A sewing machine of the character set forth in claim 1 which is adapted to be operated at a given speed and in which said stitch forming elements include a needle bar and a rotary hook, connections from said first shaft including gears arranged to drive said rotary hook, and connections from said second shaft for operating said needle bar, the exibility of said at least one ilexible member being such as to provide said first shaft and the driving connection therefor with a natural resonant frequency corresponding to a speed below said given speed.

5. A sewing machine of the character set forth in claim 1 in which said means intercoupling said shafts comprises a gear train having a rst gear mounted on and rigidly affixed -to said second shaft, a second gear freely mounted on said first shaft, a member xedly mounted on said rst shaft in spaced relation to said second gear and spring means intercoupling said second gear and said member, said spring means being constructed and arranged to introduce sufficient exibility into said means for intercoupling said shafts to provide said first shaft and Ithe driving connection therefor with a resonant frequency between 1A and 3/8 of the frequency 'of said periodic reversals of force, thereby :to isolate said iirst shaft from said second shaft with respect to torsional vibrations created by said periodic reversals of torsional force.

6. A sewing machine of the character set forth in claim S lin which said spring means comprises a plurality of spring rods and in which the mass and form of said member tixedly mounted on said first shaft are such as to add substantially to the inertia of said rst shaft.

7. A sewing machine of the character set forth in claim 1 in which said means intercoupling said shafts comprises a gear train having a first gear mounted on and rigidly afxed to said second shaft, a second gear freely mounted on said rst shaft, a disc member iixedly mounted on said first shaft in spaced relation to `said second gear and a resilient ring-like member intercoupling said second gear and said dise member, the mass and form of said disc member being such as to add substantially to the inertia of said second shaft, and said resilient member and the mass of said disc member serving to drop the resonant frequency of said first shaft and its associated elements to less than half the frequency of said periodic reversals of force, thereby to isolate said first shaft from said second shaft with respect .to torsional vibrations created by said periodic reversals of torsional force.

8. A sewing machine of the character set forth in claim 1 in which said intercoupling means comprises means comprising at least one fiexible element and a mass, said mass being such as to add substantially to the inertia of said .sec-ond shaft, and said at least .one flexible element and mass being such as to drop the resonant frequency of said second shaft and its associated elements and mass to materially less than half the frequency of said periodic reversals of force.

References Cited in the tile of this patent UNITED STATES PATENTS 95,396 Weiner Sept. 28, 1869 213,391 CleminShaW Mar. 18, 1879 1,232,922 Hobbs July l0, 1917 1,548,458 Grieb Aug. 4, 1925 1,640,670 Schaeffer Aug. 30, 1927 1,804,906 Wemp May 12, 1931 2,097,246 Christensen Oct. 26, 1937 2,329,484 Quist Sept. 14, 1943 2,444,904 Worley July 6, 1948 2,633,008 Tocci-Guilbert Mar. 31, 1953 FOREIGN PATENTS 36,686 Austria Mar. 26, 1909 

